Increased alpha3-fucosylation of alpha1-acid glycoprotein in Type I diabetic patients is related to vascular function

Diabetic mellitus is attended by the development of endothelial dysfunction which is suggested to be accompanied with a chronic low-degree of inflammation. During a chronic hepatic inflammatory response, specific changes in glycosylation of the acute phase protein ₁-acid glycoprotein (AGP) can be detected. In this report we studied the changes in glycosylation of AGP in more detail and evaluated the relation between a change in glycosylation of AGP and urinary albumin secretion in Type I diabetic patients. The glycosylation of AGP, studied by crossed affinity immunoelectrophoresis (CAIE) and high pH anion exchange chromatography with pulse amperometric detection (HPAEC-PAD), showed an increase in 3-fucosylation. Staining with an antibody against sialyl Lewis^x (sLe^x) implied that part of the 3-fucosylation was present in a sLe^x-conformation. In the group of Type I diabetic patients with increased urinary albumin excretion, a significant increase in 3-fucosylation of AGP (p[emsp4 ]<[emsp4 ]0.0005) could be detected. Therefore, the increased 3-fucosylation of AGP can be used as an additional marker for the development of vascular complications in Type I diabetic patients.     

Evidence for polynuclear iron(III) clusters in the root nodule bacterium, Rhizobium leguminosarum bv. viciae WSM710

Cells of the root nodule bacterium Rhizobium leguminosarum bv. viciae WSM710 were cultured in a medium containing 20 M ⁵⁷Fe. Mössbauer spectra of the cells at 5.5 and 3.7 K indicated that the major form of iron present in the cells was in the form of polynuclear iron(III) clusters. At 5.5 K the spectral component associated with these clusters was in the form of a superposition of a broad feature (large magnetic hyperfine field distribution) and a doublet. On lowering the temperature of the cells to 3.7 K, the spectral component was transformed into resolved magnetic hyperfine field splitting which yielded a magnetic hyperfine field of 42.4 T when fitted with broad Lorentzian peaks. These spectral characteristics are typical of the hydrated iron(III) phosphate cores of several bacterioferritins. A small fraction (11%) of the Mössbauer spectral area of the cells was in the form of a doublet which yielded parameters ( = 1.35 mm/s; E_Q = 3.15 mm/s) indicative of iron(II). The parameters are very similar to those of a spectral component previously observed in several other microbes (R. Böhnke and B.F. Matzanke (1995) BioMetals 8, 223-230) and which has been associated with a 2.2 kDa oligomeric iron(II) carbohydrate phosphate     

Frequency of human Aγ75Thr globin chain in a population from Tunisia

Summary Cord blood samples, collected at Sousse and Monastir, from Tunisian newborns were focused on a thin layer of agarose in order to detect the carriers of the ^A75Thr chain (^A chain bearing a replacement IleThr at position 75). Nineteen individuals (10%) were positive for this variant. The frequency of the ^A75Thr gene in the Tunisian population (0.050) is compared with that of various ethnic populations.This work was supported in part by the Faculté de Pharmacie et de Médecine Dentaire of Monastir and by a grant from the Ambassade de France in Tunisia     

Light-dependent chlorophyll a biosynthesis upon chlL deletion in wild-type and photosystem I-less strains of the cyanobacterium Synechocystis sp. PCC 6803

Part of the chlL gene encoding a component involved in light-independent protochlorophyllide reduction was deleted in wild type and in a photosystem I-less strain of Synechocystis sp. PCC 6803. In resulting mutants, chlorophyll biosynthesis was fully light-dependent. When these mutants were propagated under light-activated heterotrophic growth conditions (in darkness except for 15 min of weak light a day) for several weeks, essentially no chlorophyll was detectable but protochlorophyllide accumulated. Upon return of the chlL ^- mutant cultures to continuous light, within the first 6 h chlorophyll was synthesized at the expense of protochlorophyllide at a rate independent of the presence of photosystem I. Chlorophyll biosynthesized during this time gave rise to a 685 nm fluorescence emission peak at 77 K in intact cells. This peak most likely originates from a component different from those known to be directly associated with photosystems II and I. Development of 695 and 725 nm peaks (indicative of intact photosystem II and photosystem I, respectively) required longer exposures to light. After 6 h of greening, the rate of chlorophyll synthesis slowed as protochlorophyllide was depleted. In the chlL ^- strain, greening occurred at the same rate at two different light intensities (5 and 50 E m^-2s^-1), indicating that also at low light intensity the amount of light is not rate-limiting for protochlorophyllide reduction. Thus, in this system the rate of chlorophyll biosynthesis is limited neither by biosynthesis of photosystems nor by the light-dependent protochlorophyllide reduction. We suggest the presence of a chlorophyll-binding chelator protein (with 77 K fluorescence emission at 685 nm) that binds newly synthesized chlorophyll and that provides chlorophyll for newly synthesized photosynthetic reaction centers and antennae.     

Conformational study of a native monodisulfide bridge analogue of EETI II

Trypsin inhibitor EETI II, possessing six cysteinesengaged in three disulfide bridges, shares a commonstructural motif with other proteins of differentorigins and functions. To understand the principlesthat govern folding of this largely distributed basicscaffold, mainly composed of a small triple-stranded-sheet, we have studied different stages in thefolding of EETI II. The conformational properties ofa synthetic analogue of EETI II possessing only onenative (15-27) disulfide bridge were investigated withthe combined use of ¹H NMR and molecularmodelling. Although two native-like reverse turns wereobserved, formation of -sheet could not beevidenced in the one disulfide analogue, while themotif has been shown to be present in a foldingintermediate with two native disulfide bridges (9-21and 15-27). These results suggest that the structuralmotif requires stabilisation by two disulfide bridges     

Different properties of two brain extracts separated in sephadex G-50 that modify synaptosomal ATPase activities

We have previously reported that Na⁺,K⁺-ATPase of nerve ending membranes is stimulated by catecholamines only in the presence of a brain soluble fraction. The filtration of this soluble fraction through Sephadex G-50 permitted the separation of two extracts of maximal UV absorbance (peaks I and II) which showed different effects on ATPases. Peak I stimulated both Na⁺,K⁺-ATPase and Mg²⁺-ATPase activities and peak II inhibited Na⁺,K⁺-ATPase activity. We have now studied the activity of ATPases in the presence of the whole eluate obtained from the Sephadex G-50 column. It was observed that maximal effects on ATPases were obtained with peaks I and II. Peak I and peak II fractions were unable to modify the activity of acetylcholinesterase or 5-nucleotidase present in the synaptosomal membranes. The stimulatory effect of peak I on ATPases was concentration dependent (up to 1100), it was stable at different pHs and it was reverted by catecholamines. The inhibitory effect of peak II on Na⁺,K⁺-ATPase was concentration dependent (up to 150,000), it was stable only at acid pH, and it was partially reverted by catecholamines. These findings indicate that the factors responsible for the effects of peaks I and II have different properties and that their actions on ATPases show enzyme specifity.     

Characterization of a Synechococcus sp. strain PCC 7002 mutant lacking Photosystem I. Protein assembly and energy distribution in the absence of the Photosystem I reaction center core complex

A Synechococcus sp. strain PCC 7002 psaAB::cat mutant has been constructed by deletional interposon mutagenesis of the psaA and psaB genes through selection and segregation under low-light conditions. This strain can grow photoheterotrophically with glycerol as carbon source with a doubling time of 25 h at low light intensity (10 E m^–2 s^–1). No Photosystem I (PS I)-associated chlorophyll fluorescence emission peak was detected in the psaAB::cat mutant. The chlorophyll content of the psaAB::cat mutant was approximately 20% that of the wild-type strain on a per cell basis. In the absence of the PsaA and PsaB proteins, several other PS I proteins do not accumulate to normal levels. Assembly of the peripheral PS I proteins PsaC,PsaD, PsaE, and PsaL is dependent on the presence of the PsaA and PsaB heterodimer core. The precursor form of PsaF may be inserted into the thylakoid membrane but is not processed to its mature form in the absence of PsaA and PsaB. The absence of PS I reaction centers has no apparent effect on Photosystem II (PS II) assembly and activity. Although the mutant exhibited somewhat greater fluorescence emission from phycocyanin, most of the light energy absorbed by phycobilisomes was efficiently transferred to the PS II reaction centers in the absence of the PS I. No light state transition could be detected in the psaAB::cat strain; in the absence of PS I, cells remain in state 1. Development of this relatively light-tolerant strain lacking PS I provides an important new tool for the genetic manipulation of PS I and further demonstrates the utility of Synechococcus sp. PCC 7002 for structural and functional analyses of the PS I reaction center.Abbreviations ATCC American type culture collection - Chl chlorophyll - DCMU 3-(3,4-dichlorophyl)-1,1-dimethylurea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - HEPES N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid] - PCC Pasteur culture collection - PS I Photosystem I - PS II Photosystem II - SDS sodium dodecyl sulfate     

The structures of polysaccharides and glycolipids of Aspergillus fumigatus grown in the presence of human serum

A study was made of polysaccharides and glycosphingolipids isolated from Aspergillus fumigatus grown in media supplemented with human serum from healthy donors. Fractionation of Cetavlon-precipitated polysaccharides on Sephacryl S-400 gave rise to an excluded fraction (Fraction I) with molecular weight of >400 kDa and an included peak (Fraction II) with an average molecular weight of 30–80 kDa. Fraction I comprises about 5% of total polysaccharide and was identified as a glycogen-like molecule. Its structure was deduced from methylation data, treatment with amyloglucosidase, a red-brown coloration produced with an iodine solution and by ¹H and ¹³C-NMR spectroscopy. It was previously suggested that higher amounts of glycogen-like polysaccharide (20%) were present in A. fumigatus grown in serum-free medium. Fraction II was identified as a galactomannan and was the main polysaccharide of A. fumigatus grown in serum-supplemented medium. Its structure was elucidated mainly by ¹³C-NMR spectroscopy combined with partial acetolysis and methylation analysis. The ¹³C-NMR spectrum of the galactomannan showed a much greater complexity in the -d-galf and -d-manp C-1 regions, than was evident for galactomannan from serum-free cultures previously described, reflecting differences in the glycosylation pattern, stimulated in serum-supplemented medium.No differences in A. fumigatus glycosphingolipid could be detected between serum-containing and serum-free growth conditions.Our results demonstrate that the change in polysaccharide structure is a more specific response to the altered growth conditions and not merely a symptom of more general changes.This revised version was published online in October 2005 with corrections to the Cover Date.     

β-Globin gene polymorphism in the Saudi Arab population

Summary DNA mapping with the restriction endonucleases, Hpa I and Mst II, has been used to investigate -globin gene polymorphism in the Saudi Arab population. Using Hpa I digestion, 13.0kb and 7.6kb fragments were found in association with the ^A and ^S genes. The frequency of the polymorphic forms in two regions investigated vary significantly. In Al-Hafouf and the surrounding villages, situated in the Eastern Province of Saudi Arabia, the frequencies of association of the ^S gene with the Hpa I 7.6kb, 7.0kb, and 13.0kb fragments were 0.866, 0.043, and 0.071, respectively. The frequency of association of ^A with the 7.6kb and 13.0kb fragments resulting from the Hpa I digestion were 0.875 and 0.125. In Khaiber, Tehamat-Aseer, and surrounding villages, in the Western Province, the frequency of association of ^S with 7.6kb, 7.0kb, and 13.0kb fragments were 0.836, 0.027, and 0.0136, respectively, while that of ^S was 0.250 and 0.750 with 7.0kb and 13.0kb Hpa I fragments, respectively. Using Mst II digestion, ^A was found to be linked to a 1.15kb fragment, while ^s was linked to a 1.35kb fragment. The normal (Hb AA), heterozygotes (Hb AS), and homozygotes (Hb SS) gave 1.15, 1.15/1.35, and 1.35kb fragments, respectively. The results of this study show extensive polymorphism at the Hpa I restriction site of the ^A and ^S globin genes with the different polymorphic forms existing at a variable frequency in different regions of Saudi Arabia.     

Identification of the oligosaccharide structures of human coagulation factor X activation peptide at each glycosylation site

Human blood coagulation factor X has two N-linked oligosaccharides at Asn³⁹ and Asn⁴⁹ residues and two O-linked oligosaccharides at Thr¹⁷ and Thr²⁹ residues in the region of the factorX activationpeptide (XAP) which is cleaved off during its activation by factor IXa. We determined the structure of oligosaccharides in the XAP region of human factor X. Four glycopeptides each containing a glycosylation site were isolated by digestion of XAP with endoproteinase Asp-N followed by reversed-phase HPLC. N-linked oligosaccharides released from the glycopeptides by glycoamidase A digestion were derivatized with 2-aminopyridine. Pyridylamino(PA)-oligosaccharides were separated by HPLC into neutral and sialyl oligosaccharides using an anion-exchange column. Structures of oligosaccharides and their contents at each glycosylation site were determined by a two-dimensional sugar mapping method. The contents of the neutral oligosaccharides at Asn³⁹ and Asn⁴⁹ residues were 32.5% and 30.0%, respectively. Six neutral and twelve monosialyl oligosaccharides isolated from both N-linked glycosylation sites showed similar elution profiles composed of bi-, tri-and tetra-antennary complex type oligosaccharides. The predominant component in neutral oligosaccharides was biantennary without a fucose residue. Two major monosialyl oligosaccharides were also biantennary without fucose and with a Neu5Ac-26 residue. In addition, the structures of O-linked oligosaccharides at Thr¹⁷ and Thr²⁹ residues were suggested to be disialylated Gal/3GalNAc sequences by their component analyses.Abbreviations Gal d-galactose - GlcNAc N-acetyl-d-glucosamine - Man d-mannose - HPLC high-performance liquid chromatography - NDV Newcastle disease virus - Neu5Ac 5-N-acetylneuraminic acid - ODS octadecylsilyl - PA pyridylamino - RVV-X Russell's viper venom factor X activator - TBS Tris-buffered saline - XAP factor X activation peptide.     

Partial purification and properties of γ-glutamyltranspeptidase from mycelia of Morchella esculenta

Three -glutamyltranspeptidase (enzymes I, II and III) were partially purified from the cell free extracts of the cultured mycelia of Morchella esculenta Fr. The molecular masses of enzymes were 155,000 (I), 219,000 (II) and 102,000 (III). All of them catalyzed both hydrolysis and transpeptidation of various -glutamyl compounds. -l-Glutamyl-cis-3-amino-l-proline occurring in the cultured mycelia of this fungus was a good substrate for both reactions. K _m values for hydrolysis were in the order of 10^-4 to 10^-5 M, and those for transpeptidation were in the order of 10^-2 to 10^-4 M. The enzymes were inhibited by a -glutamyltranspeptidase inhibitor, l-serine plus borate.Abbreviations -GTP -glutamyltranspeptidase - HPLC High-performance liquid chromatography     

Phosphorylation of the 24p3 protein secreted from mouse uterus in vitro and in vivo

The 24p3 protein is a 25 KDa glycoprotein, having been purified from mouse uterine fluid. Thr⁵⁴, Ser⁸⁸, and Thr¹²⁸/Ser¹²⁹ on the protein molecule were predicted to be the phosphorylation site of casein kinase II, protein kinase C, and cAMP-dependent protein kinase, respectively. Incorporation of phosphate to this protein from [-³²P]-ATP was tested in the solution suitable for the three kinases. Neither casein kinase II nor cAMP-dependent protein kinase reacted to the 24p3 protein; however, protein kinase C demonstrated phosphorylation to this protein. This phosphorylation may be competing with a polypeptide segment: Arg⁷⁹-Tyr-Trp-Ilu-Arg-Thr-Phe-Val-Pro-Ser⁸⁸-Ser-Arg-Ala-Gly-Gln-Phe-Thr-Leu-Gly⁹⁷ in the 24p3 protein molecule. To support this theory, Ser⁸⁸ is a phosphorylation site of protein kinase C on 24p3 protein. The enzyme kinetic parameter, based on the Michaelis-Menten equation, determined Km to be 2.96 M in the phosphorylation of 24p3 protein by the kinase. Both of the phosphorylated and dephosphorylated form of 24p3 protein can enhance the cAMP-dependent protein kinase activity in vitro. In addition, this experiment will show for the first time that serine-phosphorylated 24p3 protein exists in mouse uterine tissue.     

Isolation and characterization of β-glucosidases from Aspergillus nidulans mutant USDB 1183

Two extracellular -glucosidases (cellobiase, EC 3.2.1.21), I and II, from Aspergillus nidulans USDB 1183 were purified to homogeneity with molecular weights of 240,000 and 78,000, respectively. Both hydrolysed laminaribiose, -gentiobiose, cellobiose, p-nitrophenyl--L-glucoside, phenyl--L-glucoside, o-nitrophenyl--L-glucoside, salicin and methyl--L-glucoside but not -linked disaccharides. Both were competitively inhibited by glucose and non-competitively (mixed) inhibited by glucono-1,5-lactone. -Glucosidase I was more susceptible to inhibition by Ag⁺ and less inhibited by Fe²⁺ and Fe³⁺ than -glucosidase II.     

Internal motions of apo-neocarzinostatin as studied by 13C NMR methine relaxation at natural abundance

Summary Dynamics of the backbone and some side chains of apo-neocarzinostatin, a 10.7 kDa carrier protein, have been studied from ¹³C relaxation rates R1, R2 and steady-state ¹³C-{¹H} NOEs, measured at natural abundance. Relaxation data were obtained for 79 nonoverlapping C resonances and for 11 threonine C single resonances. Except for three C relaxation rates, all data were analysed from a simple two-parameter spectral density function using the model-free approach of Lipari and Szabo. The corresponding C–H fragments exhibit fast (_e < 40 ps) restricted libration motions (S²=0.73 to 0.95). Global examination of the microdynamical parameters S² and _e along the amino acid sequence gives no immediate correlation with structural elements. However, different trends for the three loops involved in the binding site are revealed. The -ribbon comprising residues 37 to 47 is spatially restricted, with relatively large _e values in its hairpin region. The other -ribbon (residues 72 to 87) and the large disordered loop ranging between residues 97–107 experience small-amplitude motions on a much faster (picosecond) time scale. The two N-terminal residues, Ala¹ and Ala², and the C-terminal residue Asn¹¹³, exhibit an additional slow motion on a subnanosecond time scale (400–500 ps). Similarly, the relaxation data for eight threonine side-chain C must be interpreted in terms of a three-parameter spectral density function. They exhibit slower motions, on the nanosecond time scale (500–3000 ps). Three threonine (Thr⁶⁵, Thr⁶⁸, Thr⁸¹) side chains do not display a slow component, but an exchange contribution to the observed transverse relaxation rate R2 could not be excluded at these sites. The microdynamical parameters (S², _e and R2_ex) or (S _infslow ^sup2 , S _inffast ^sup2 and _slow) were obtained from a straightforward solution of the equations describing the relaxation data. They were calculated assuming an overall isotropic rotational correlation time _e for the protein of 5.7 ns, determined using standard procedures from R2/R1 ratios. However, it is shown that the product (1–S²)× _e is nearly independent of _e for residues not exhibiting slow motions on the nanosecond time scale. In addition, this parameter very closely follows the heteronuclear NOEs, which therefore could be good indices for local fast motions on the picosecond time scale.     

Fine structure,origin, and distribution density of the autonomic nerve endings in the tarsal muscle in the eyelid of the mouse

Summary The fine structure, origin, and distribution density of the autonomic nerve endings in the tarsal muscle of the mouse were studied by histochemistry and electron microscopy. With histochemical methods, the fine nerve plexus in the normal muscle shows both catecholamine-positive varicose fibers and acetylcholinesterase-active varicose fibers. The former are distributed more densely than the latter. After superior cervical ganglionectomy, the catecholamine-positive fibers disappear, while after pterygopalatine ganglionectomy, the acetylcholinesterase-active fibers vanish. In electron micrographs, the varicosities appear as expansions containing many synaptic vesicles. The axonal expansions partly lack a Schwann sheath and directly face the pinocytotic vesicle-rich zones of the smooth muscle cells. A relatively wide space, 0.1 to 1.0 m in width, lies between nerve expansion and muscle cell. The expansions can be classified into two types: Type I having small granular synaptic vesicles, and Type II having agranular vesicles instead of small granular synaptic vesicles. Type I undergoes degeneration after superior cervical ganglionectomy, while Type II degenerates after pterygopalatine ganglionectomy. This indicates that Type I corresponds to the synaptic ending of the adrenergic fiber originating from the superior cervical ganglion, and Type II to the synaptic ending of the cholinergic nerve fiber derived from the pterygopalatine ganglion. Type I is more frequent (88/10⁴ m² area of muscle) than Type II (17/10⁴ m²).     

Biochemical characterization of theO-glycans on recombinant glycophorin A expressed in Chinese hamster ovary cells

Alterations inN- andO-linked glycosylation affect cell surface expression and antigenicity of recombinant glycophorin A expressed in transfected Chinese hamster ovary (CHO) cells. To understand these effects further, glycophorin A was purified by immunoaffinity chromatography from transfected wild type and glycosylation deficient CHO cells. TheO-glycans were characterized both biochemically, using gel filtration and high performance anion exchange chromatography, and immunologically, using carbohydrate specific monoclonal antibodies to probe Western blots. TheO-glycans of human erythrocyte glycophorin A consist mainly of short oligosaccharides with one, two, or three sialic acid residues linked to a common disaccharide core, Gal1-3GalNAc1-Ser/Thr, with the disialylated structure being the most abundant. With the exception of the trisialylated derivative, the same structures were found on recombinant glycophorin A expressed by wild type CHO cells. However, in contrast to human crythrocyte glycophorin A, the monosialylated oligosaccharide was the most abundant structure on the recombinant protein. Furthermore, recombinant glycophorin A was shown to express a small amount of the Tn antigen (GalNAc1-Ser/Thr). Recombinant glycophorin A had the sameO-glycan composition, whether purified from clones expressing high or moderate levels of the recombinant glycoprotein. This indicates that the level of expression of the transfected glycoprotein did not affect itsO-glycan composition. Deletion of theN-linked glycosylation site at Asn₂₆, by introducing the Mi.I mutation (Thr₂₈ Met) by site-directed mutagenesis, did not markedly affect theO-glycan composition of the resulting recombinant glycoprotein expressed in wild type CHO cells. This demonstrates that the presence or absence of theN-glycan did not influenceO-linked glycosylation of the recombinant glycoprotein. Finally, theO-glycans on recombinant glycophorin A expressed in the Lec 2 and Lec 8 glycosylation deficient CHO cells were characterized. TheO-glycans on Lec 2 cell glycophorin A were predominantly Gal1-3GalNAc1-Ser/Thr (T antigen), while those on Lec 8 glycophorin A were exclusively GalNAc1-Ser/Thr (Tn antigen). These results will lead to a better understanding of the cell biology and immunology of this important human erythrocyte glycoprotein.     

Horseradish peroxidase C

Summary Horseradish peroxidase C (HRP; ferric) reacts with H₂O₂ to form Compound I, with an equilibrium constant of about 10¹⁴ M^–1. Two-step reduction of Compound I to Compound II and further to the ferric enzyme occurs reversibly at E_o values of 0.90 and 0.93 V (pH 7.0), respectively. The pH dependence of E_o values for each one-electron step, ferrous ferric Compound II Compound I indicates the presence of redox-linked ionization at pK_a values of 7.3 in the ferrous state, 11.0 in the ferric and 8.6 in Compound II. Zinc-substituted HRP C is oxidized to its free-radical form at an E_o value of 0.74 (pH 6.0). Comparison of oxidized zinc HRP C with Compound I shows that Compound I contains a porphyrin -cation radical. The flash photolysis study on the NO-ferric HRP C complex clearly indicates that the iron is pentacoordinated in HRP C while it is hexacoordinated in metmyoglobin. From the kinetic analysis of the acid-alkaline conversion of HRP C, the second-order rate constants of the reactions with H⁺ and HO^– are estimated to be 1.5 × 10¹⁰ and 6.7 × 10⁴ M^–1s^–1, respectively. The latter rate constant greatly varies with the kind of hemoproteins. In the presence of HRP C and O₂, indole-3-acetate is oxidized to its hydroperoxide form, which reacts effectively with HRP C to form Compound I and further converts Compound I to a verdohemoprotein.Abbreviations HRP horseradish peroxidase (HRP without subgroup letter denotes a classical preparation consisting of HRP B and HRP C) - EPR electron paramagnetic resonance - NMR nuclear magnetic resonance     

Adaptation of the thylakoid membranes of pea chloroplasts to light intensities. II. Regulation of electron transport capacities,electron carriers,coupling factor (CF1) activity and rates of photosynthesis

The electron transport rates of photosystems II and I, amounts of electron carriers, coupling factor activity and photosynthetic rates were investigated in thylakoids isolated from pea plants grown under a wide range of light intensities (16 h light-8 h dark). The electron transport rates of PS II and PS I, as partial reactions or in whole chain, and coupling factor activity on a unit chlorophyll basis, all increased as the light intensity available for growth was altered from a very low intensity of 10 E m^-2s^-1 to a high intensity of 840 E m^-2s^-1. Similarly, there were increases in the amounts of atrazine binding sites, plastoquinine, cytochrome f and P700 per unit chlorophyll; significantly, the amounts of reaction centres of PS II and PS I were not equal at any light intensity. The rate of change of all parameters with respect to light intensity could be represented by two straight lines of different slopes which met at a transition point corresponding to approximately 200 E m^-2s^-1 during growth. These photoadaptations were similar to those observed for both the relative distribution of chlorophyll in chlorophyll-protein complexes and the chl a/chl b ratios [Leong and Anderson, 1984, Photosynthesis Research 5:117–128]. Since these thylakoid components and functions were affected in the same direction by light intensity during growth and all show linear relationships with chl a/chl b ratios, it indicates that they are closely regulated and markedly well co-ordinated. Plants compensate for the limited amount of low light intensities by drastically increasing the light-harvesting antenna unit size of photosystem II and to a lesser extent that of photosystem I. Changes in the composition of the thylakoid membranes exert a regulatory effect on the overall photosynthetic rate up to approximately 450 E m^-2s^-1.Abbreviations chl chlorophyll - cyt cytochrome - PQ plastoquinone - PS photosystem     

An epitope common to HLA class I and class II antigens,Ig light chains,and β 2-microglobulin

The homology of class I major histocompatibility complex (MHC) antigens, class II MHC antigens, and immunoglobulin molecules has suggested their divergence from a common ancestral gene. We report here a monoclonal antibody (mAb), PAC. M1, which reacts with HLA class I heavy chains, HLA class II and chains, and the light chain of human immunoglobulin by Western blot analysis. PAC.M1 reacted with 44 kd, 33 kd, and 29 kd species when tested on membrane glycoproteins from TRa1, a B-lymphoblastoid cell line (B-LCL). Two-dimensional electrophoresis and Western blotting of TRa1 glycoproteins showed that these species had the appropriate electrophoretic mobilities for class I heavy chain and class II and subunits. The presence of the epitope was verified on class II and subunits by Western blotting of purified -invariant chain complexes, and on class I heavy chains by Western blotting of purified class I antigens. The PAC. M1 mAb also reacted with immunoglobulin light chains when Western blotting was performed with normal human serum and purified IgG and IgM as antigens. While reactivity of the mAb with beta-2 microglobulin ( ₂m) was difficult to detect by Western blotting, binding of PAC.M1 to purified ₂m was detectable in a solid-phase binding assay. Thus, PAC.Ml reacts with a determinant shared by a number of members of the immunoglobulin superfamily.